We've always assumed that non-shift movement was safe, as long as it was movement between squares adjacent to the enemy. The way we've played it, only movement from an adjacent square to a non-adjacent square provoked OA.

(I have no idea how this misconception has managed to survive for this long. Reading the compendium entry and the Player's Handbook, the rules are perfectly clear and even simpler and more logical that what we've been doing.)

My question is, should I correct the group, or should we keep playing the way we've done?

Apart from just having to adjust to this mechanic, combat is probably going to change somewhat. Flanking will become harder to achieve (something we've always taken for granted - two of the players even got the Eyes in the Back of Your Head feat to avoid getting flanked), safe movement will be more expensive, shifting more valuable and threatening reach a lot more threatening - melee characters won't even be able to attack it without provoking OAs (actually, I've always wondered why there weren't more monsters with this property).

Also, always a good advice: talk with them :) Tell them that you realized you messed up the AoO thing, and it works this way and not that way. Ask them what they think, and go with it.
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Cristol.GdMJan 21 '13 at 16:31

Just FYI, the AoO system you've described (where you can move around a foe but not away from him) is how the equivalent rule work in Savage Worlds. So if any of you've played that prior to 4E, maybe that's where your misconception came from.
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Joe BedurndurnJan 22 '13 at 8:24

2 Answers
2

D&D is a consensus game - Discuss the Options

Your problem is not unique - it happens to every game master with a new system. It even happens in board games. It also happens whenever there is errata - changing the "offical rules."

But, you are playing with a group of people so you should discuss any rule changes with the rest - regardless of the the reason. I'm sure you also have adapted to this style of play - perhaps making encounters more challenging in other ways...

When talking about it with your group - offer several options:

Adopt the official rules: Use BESW's excellent answer here for that approach.

House-rule your existing method as a special kind of shift and add monster powers that trigger on shift (there are many in the compendium) - at least to your skirmishers.

House-rule your existing interpretation and don't change a thing. After all, you're all having fun this way.

Change to official rules at your next big break. Assuming you continue with a house-rule choice, you can all agree that you'll mix it up when you start your next batch of characters or between major campaign story arcs.

The option: "Keep this to yourself" isn't there because it is a disservice to your players, who - if they ever play 4e with another group are going to be very disappointed that their build/tactics don't work. Everyone should know the official rules, even if they are being modified.

The crux of this answer "be open and honest and discuss with positive suggestions" is a great answer for all sorts of situations
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Simon WithersJan 21 '13 at 21:15

2

Seems the more sensible answer to me. Do whatever makes you and your player happier. Also, you can always try it for one session and go back to your house rule if the group doesn't like it.
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FlammaJan 22 '13 at 8:46

Yes, use the actual rules now that you know them

The game is balanced around the ruleset it assumes is in use, and as you've already noticed any change to the rules is going to have system-wide implications (in this case, some very significant ones). You'll find a lot of powers, items, feats, and design philosophies make more sense now.

But allow massive re-training

Your group has been building on an erroneous assumption, and it would be cruel to penalize them for building within the rules they were using. When you make this change, give them at least a week's notice to retrain/rebuild their characters, just as I assume you would do if someone's character was based on a rule that got significantly errata'd.

I think you'll like it

The 4e combat system is centered on movement and forcing bad choices on your enemies. The opportunity attack rules will make it much easier for your characters to force bad choices on their enemies just by standing near them. The OA rules also make the many movement-based powers available to players even more enticing and enjoyable, as you dance around your enemies in blatant defiance of The Way Things Should Be.